1. Field of the Invention
The present invention relates to a data sector reassigning technique in a hard disk drive, and a disk surface using SMART (Self Monitoring Analysis & Reporting Technology).
2. Description of the Related Art
In a hard disk drive used as an auxiliary memory device of a computer system, growable soft defects are beforehand detected from a data sector, and another normal data sector is reassigned to substitute for the defective data sector. This is called automatic reassignment. Detection of the growable soft defects is performed mainly by varying an ECC (Error Correction Code) correction capability. In this method, data is read with a low ECC correction capability in an early stage. If an ECC error is generated during the data read, it is determined whether the error is recovered by an error recovery routine. If the error is not recovered, the ECC correction capability is set to a maximum and the data is re-read. Then, if the data is read without any error, the read data is written in a remapped, that is, reassigned data sector.
However, the above method has the following drawbacks. Data sectors having growable soft defects cannot be accurately estimated because the ECC correction capability is set to a maximum without consideration of head performance or disk characteristics. Hence, too many data sectors unnecessarily turn out defective. That is, assuming that a normal ECC correction capability is 1, a maximum ECC correction capability is 2, and an error rate increases at the ECC correction capability of 1, the ECC correction capability is set to 2 according to the above method. As a result, data sectors having soft defects unlikely to grow are determined to be defective sectors, lowering the total performance of the drive.
The following patents each disclose features in common with the present invention but do not teach or suggest the technique for reassigning a data sector by detecting a soft defect as in the present invention: U.S. Pat. No. 5,237,553 to Fukushima et al, entitled Data Recording And Reproducing Apparatus Having A Plurality Of Operating Modes, and U.S. Pat. No. 5,150,050 to Genheimer et al., entitled Adaptive Variable Threshold Qualification Level Circuit For Signal Processing In Disk Drives.